Biology Forums - Study Force

cells composing organ?

pump variables/variables of minute?

Inhale: this is bringing air into the lungs, your body does this by creating a negative pressure in your chest, so air rushes in to equalize it. It creates a negative pressure by increases the volume of the best. Your diaphragm contracts and pulls downward, and your intercostal muscles between the ribs contract and lift and widen the rib cage.

Exhale: this is pushing air out of your lungs, and surprisingly is a very passive activity. The easiest way to force air out is to reduce the volume of the chest, so the muscles that contracted relax and the diaphragm returns to its original spot, and the chest wall returns to its resting position which pushes air out. Now this is during quiet breathing. For forced expiration the muscles of your back, abs and ribs contract to force the chest down faster.

It has to do with the volume of the thoracic cavity. When the diaphragm contracts, volume inside increases, and the pressure difference sinces below 1 torr or 760 mmHg. This causes air to rush in

To understand the direction of gas exchange: think of the relation between volume & pressure and between alveoli pressure & atmospheric pressure.

Inspiration- Thoracic volume increases, so thoracic (specifically alveoli) pressure decreases.  Thoracic pressure is lower than atmospheric pressure, so air enters alveoli from the atmosphere.

Expiration- Thoracic volume decreases; so, thoracic (specifically alveoli) pressure increases.  Thoracic pressure is greater than atmospheric pressure, so air exits alveoli to enter the atmosphere.